BBC Scotland answers key questions on the expenses row which forced the resignation of Scotland's First Minister Henry McLeish.

What is this Officegate row all about?

When he was a Westminster MP, Henry McLeish sub-let part of his constituency office in Glenrothes, in Fife, and failed to register the income he received with the Commons authorities.

MPs are given an allowance from the public purse to pay for office costs. The extra money Mr McLeish received from his tenants should have been offset against this allowance. This did not happen.

There has also been concern that election literature produced for Mr McLeish publicised his constituency office as a campaign headquarters against strict rules.

How has the first minister defended himself over this?

When the matter was first raised in April by the Tories, Henry McLeish started discussions with the Commons authorities and last month agreed to pay back £9,000 from his own pocket to the Westminster fees office.

As far as he was concerned, the matter was closed, but opposition politicians wanted more information.

How was the figure arrived at? How much more money had tenants paid? What was the money used for?

Mr McLeish released a detailed response on Tuesday. He said he had five tenants since the office opened in 1987, generating £36,000.

He said all the money was used on office costs to the benefit of his constituents rather than himself or his party.

The first minister asked Westminster to look at his accounts and agreed to pay back more money if necessary.

Mr McLeish had managed to persuade Labour backbenchers earlier in the week that this was a muddle and not a fiddle. He had been expected to come to parliament and make that same statement.

Why was this a resignation issue?

The Scottish National Party called for Mr McLeish's resignation, saying he has been 'fundamentally wounded'.

But prior to his dramatic resignation announcement on 8 November, Mr McLeish had intended to stay in office.

He secured the support of the Labour group in the Scottish Parliament, as well as the Liberal Democrats - partners with Labour in the Scottish Executive.

The Conservatives set aside time on 8 November for a full debate at Holyrood on an affair some observers felt had reduced his standing with politicians and the public, leaving him a weakened leader.

Personally Mr McLeish feels he has had enough and had begun to bring the Labour Party and the Scottish Parliament into disrepute.

Was Mr McLeish forced to resign?

It is understood that he took the decision himself after overnight consultations with senior executive ministers and officials. He also spoke to both Numbers 10 and 11 Downing Street, who questioned if he really needed to go.

Who was Mr McLeish's office sub-let to and how much did they pay?

There have been five tenants in the part of the Glenrothes constituency office which was sub let between 1987 and 2001.

Security firm Honeywell-Shield paid £4,000 for the period from 1987 to 1989, and office equipment company Capital Solutions paid £12,000 between 1989 and 1994. Fife Council's economic development unit rented office space between 1995 and 1997 at a cost of £10,122, before solicitors Thompsons paid £1,000 between 1997 and 1998. Another solicitor's firm, Digby Brown, rented space from 1998 to 2001 and paid £9,000 - the figure which was repaid to the fees office.

What happens with a successor?

Jim Wallace, the leader of the Scottish Liberal Democrats - Labour's coalition partners at Holyrood - has been designated acting first minister until a successor is chosen.

The Labour Party will elect a leader and a successor is expected to emerge from a field that includes education minister Jack McConnell, finance minister Angus MacKay, communities minister Jackie Baillie and Wendy Alexander at enterprise.

Under the terms of the Scotland Act, there must be a First Minister within 28 days or there needs to be an election, so it will all be resolved within a month.